The present invention is directed to probe structures for testing of electrical interconnections to integrated circuit devices and other electronic components and particularly to testing of integrated circuit devices with rigid interconnection pads and multi-chip module packages with high density interconnection pads.
Integrated circuit (IC) devices and other electronic components are normally tested to verify the electrical function of the device and certain devices require high temperature burn-in testing to accelerate early life failures of these devices. Wafer probing is typically done on a single chip site at temperatures ranging from 25xc2x0 C.-125xc2x0 C. while burn-in is typically done on diced and packaged chips at temperatures ranging from 80xc2x0 C. to 150xc2x0 C. Wafer probing and IC chip burn-in at elevated temperatures of up to 200xc2x0 C. has several advantages and is becoming increasingly important in the semiconductor industry. Simultaneous testing of multiple chips on a single wafer has obvious advantages for reducing costs and increasing production throughput and is a logical step towards testing and burn-in of an entire wafer.
The various types of interconnection methods used to test these devices include permanent, semi-permanent, and temporary attachment techniques. The permanent and semi-permanent techniques that are typically used include soldering and wire bonding to provide a connection from the IC device to a substrate with fan out wiring or a metal lead frame package. The temporary attachment techniques include rigid and flexible probes that are used to connect the IC device to a substrate with fan out wiring or directly to the test equipment.
The permanent attachment techniques used for testing integrated circuit devices such as wire bonding to a lead frame of a plastic leaded chip carrier are typically used for devices that have low number of interconnections and the plastic leaded chip carrier package is relatively inexpensive. The device is tested through the wire bonds and leads of the plastic leaded chip carrier and plugged into a test socket. If the integrated circuit device is defective, the device and the plastic leaded chip carrier are discarded.
The semi-permanent attachment techniques used for testing integrated circuit devices such as solder ball attachment to a ceramic or plastic pin grid array package are typically used for devices that have high number of interconnections and the pin grid array package is relatively expensive. The device is tested through the solder balls and the internal fan out wiring and pins of the pin grid array package that is plugged into a test socket. If the integrated circuit device is defective, the device can be removed from the pin grid array package by heating the solder balls to their melting point. The processing cost of heating and removing the chip is offset by the cost saving of reusing the pin grid array package.
The most cost effective techniques for testing and burn-in of integrated circuit devices provide a direct interconnection between the pads on the device to a probe sockets that is directly connected to the test equipment. Contemporary probes for testing integrated circuits are expensive to fabricate and are easily damaged. The individual probes are typically attached to a ring shaped printed circuit board and support cantilevered metal wires extending towards the center of the opening in the circuit board. Each probe wire must be aligned to a contact location on the integrated circuit device to be tested. The probe wires are generally fragile and easily deformed or damaged. This type of probe fixture is typically used for testing integrated circuit devices that have contacts along the perimeter of the device. This type of probe is also much larger than the IC device that is being tested and the use of this type of probe for high temperature testing is limited by the probe structure and material set.
Another technique used for testing IC devices comprises a thin flex circuit with metal bumps and fan out wiring. The bumps are typically formed by photo lithographic processes and provide a raised contact for the probe assembly. The bumps are used to contact the flat or recessed aluminum bond pads on the IC device. An elastomer pad is typically used between the back of the flex circuit and a pressure plate or rigid circuit board to provide compliance for the probe interface. This type of probe is limited to flexible film substrate materials that typically have one or two wiring layers.
High density probes used for wafer probing are typically very expensive due to the complexity of the substrate or space transformer and the process used for attaching and aligning the probes to the substrate. During the useful life of a probe fixture, it is likely to be damaged due to handling or worn from normal use. In order to avoid the expense of replacing the entire test fixture (substrate and probe contacts), it is desirable to be able to repair, rework, or replace the damaged or worn probes without replacing the entire substrate.
The prior art described below includes a several different probe fixtures for testing bare IC chips.
Rework and repair techniques exist for cantilever probes that are used to test low density I/O circuit devices. The rework and repair techniques include manual reforming and repositioning the cantilever probes as well as removing and replacing individual cantilever probes attached to the test card. The rework and repair techniques are the same manual processes used to fabricate the original cantilever probe card.
Flex circuit test probe structures are also limited to testing low density I/O circuit devices and are relatively inexpensive. The flex probe interposer is usually discarded and replaced when they are worn out or become damaged.
Cobra probes are a type of compliant interposer probe that have been used to test IC devices in IBM for many years. Cobra probes have primarily been used to test IC devices with C4 solder ball connection but can be modified to test IC devices with wire bond pads. The Cobra probes are made from a Paleney 7 alloy and are housed in a machined Vespal housing. Cobra probes can be reworked and repaired as a separate operation since the probes are not attached to a test card or fanout substrate. The rework operations that are typical for a cobra probe assembly include refinishing the contact surface of the probes to remove contamination along with disassembling and replacing damaged probes.
It is the object of the present invention to provide a means of repairing, reworking, or replacing damaged probes that are formed using a xe2x80x9cflying leadxe2x80x9d wire bonding process and used for testing integrated circuit devices and other electronic components.
Another object of the present invention is to provide a means of repairing, reworking, or replacing damaged probes with the same column and row spacing as the original probes.
A further object of the present invention is to provide a means of repairing, reworking, or replacing damaged probes with the same wire geometry as the original probes.
An additional object of the present invention is to provide a means of repairing, reworking, or replacing damaged probes with the same probe height as the original probes.